In this study, changes in proliferation kinetics and regulatory control mechanisms enabling DNA synthesis and replicative activity to persist are analyzed during neoplastic transformation of gastrointestinal cells. Man, and rodents receiving carcinogens inducing gastrointestinal cancer, are studied. Findings are compared during the stages of transformation that develop in gastrointestinal cells. Relationships of kinetic and biochemical parameters during the evolution of neoplastic lesions are analyzed. BIBLIOGRAPHIC REFERENCES: Sherlock, P., Lipkin, M. and Winawer, S.J. Predisposing Factors in Colon Carcinoma, in Stollerman, G.H., ed. Advances in Internal Medicine, Vol. 20, Chicago Year Book Pub., 1975, pp. 121-150. Deschner, E. and Lipkin, M. Proliferative Patterns in Colonic Mucosa in Familial Polyposis. Cancer 35:413-418, 1975.